Abstract: Superlarge diameter shield launching with shallow overburden faces many problems such as water loss and soil erosion at portal sealing and difficult control of tunneling and segment attitudes. As a result, a case study is conducted on shield launching of Chunfeng tunnel. According to the geological and engineering conditions, the strengthened water sealing method of Ushaped plain diaphragm + triple pipe jet grouting is adopted, the sectioned breaking is adopted for portal to reduce the risk, and as well the tunneling slope is adjusted and the negative ring is fixed to guarantee the effect. Moreover, for slurry leakage phenomenon, the methods of adopting back pressure cover, increasing earth pressure on upper part, and reducing slurry chamber pressure are used to reduce uplift of ground, thus ensuring normal cycling of slurry for shield launching. Finally, a suite of superlarge diameter shield launching technology with shallow overburden is formed.

Key words: Chunfeng tunnel, superlarge diameter shield, shallow overburden, launching technology